1. Field of the Invention
The present invention relates to devices for generating electricity, and particularly to a wind turbine generator system for generating electricity by wind power.
2. Description of the Related Art
Wind power has provided a local source of energy for centuries. In the United States, the invention of the mechanical windmill in the 19th century allowed the settlement of much of the American frontier and still remains a localized source of power for farms and ranches. Beginning in the 1920's, rural families used small wind turbine electric generators to power their homes. Following the enactment of the Rural Electrification Act in the 1930's, and the creation of rural electric cooperatives for bringing dependable electric power to rural areas, governmental policies favored the design and construction of large centralized, primarily fossil-fueled fired, electric generation facilities which distributed electric power to rural areas over a large transmission and distribution grid.
These governmental policies effectively crippled the market for small wind turbine electric power generation in the United States until the oil crisis in the late 1970's. For approximately ten years following the passage of environmental laws in the late 1970's, tax credits and favorable federal regulations created a new market for small wind powered electric generation systems for rural homes, farms and ranches. When the tax credits ceased to be available and the price of oil declined in the late 1980's, small wind turbine businesses were again driven out of business.
The demand for electric power continues unabated. As a result of the rapid increase in oil and natural gas prices since the late 1990's, the growing awareness that emissions from fossil-fuel sources is the likely cause of global warming, and the need for energy independence for national security reasons, there has been an increased demand for cost-effective electric power generated from renewable resources, such as wind and solar.
In response to this demand, along with innovations in wind turbine design and efficiency, large utility-scale wind turbine electric generator farms (commonly referred to as “big wind”) have been constructed in remote areas of the country with high wind potential. This increasingly competitive source of energy is steadily providing a growing share of U.S. electricity without consuming any natural resource or emitting any pollution or greenhouse gases. Wind energy generation is growing rapidly throughout the U.S. Wind energy has been growing 29% annually from 2002 to 2007 and the installed wind energy generating capacity is now over 20,000 MW (estimated by the end of 2008). Wind power currently supplies 1% of the nation's electricity, but is estimated to be capable of providing as much as 20% by 2020.
When most Americans think of wind power, they think of “big wind”. Big wind power is generated by utility scale turbines. Many of these wind turbines have blades over 40 meters wide, meaning the diameter of the rotor is over 80 meters (nearly the length of a football field), mounted on towers 80 meters tall. These types of turbines can produce 1.8 Megawatts (MW) of power. The current wind farm model is to place a large number of these utility scale wind turbines in one central location.
Such “big wind” farms, however, have disadvantages. The wind turbines are very expensive and must also be located in areas of high wind potential. Land for the wind farm has to be purchased or leased. In addition, the big wind developer has to purchase transmission line easements from the wind farm to the existing transmission power grid. As a result, the development time is long and costs are very high. Because of these restrictions, many new big wind farms cannot be built for six to ten years.
In addition, such big wind farms are typically located remotely from the large urban areas experiencing the most rapid growth in the demand for electricity. The transmission of such big wind-generated electric power over long distances has taxed the existing transmission grid to its limits, thereby adding to the nation's already most pressing energy and electric power problems, including blackouts and brownouts, energy security concerns, power quality issues, tighter emissions standards, transmission bottlenecks, and the desire for greater control over energy costs.
These transmission grid problems have constrained the development of big wind farms until either developers or governmental entities build new transmission capacity over long distances. This will require both huge capital investment and very long development cycles because of the need to purchase additional “rights-of-way” or easements for the new transmission lines. Such delays and capital investment substantially increase the per KWH costs of energy to the consumer, thereby making “big wind” generated electric power more expensive.
Smaller scale wind generation is also known and is typically also based on turbine driven power. However, typical wind driven turbines are relatively inefficient, often only converting a small fraction of the wind's kinetic energy into usable electrical power, and also only being effective when the wind is blowing in one particular direction within a small range of desirable speeds.
Thus, a wind turbine generator system solving the aforementioned problems is desired.